The specimen holder is a component of an electron microscope providing the physical support for specimens under observation. Specimen holders traditionally used for TEMs and STEMs, as well as some modern SEMs, consist of a rod that is comprised of three key regions: the end (300), the barrel (200) and the specimen tip (100) (see, e.g., FIG. 1). In addition to supporting the specimen, the specimen holder provides an interface between the inside of the instrument (i.e., a vacuum environment) and the outside world.
To use the specimen holder, one or more samples are first placed on a specimen support device. The specimen support device is then mechanically fixed in place at the specimen tip, and the specimen holder is inserted into the electron microscope through a load-lock. During insertion, the specimen holder is pushed into the electron microscope until it stops, which results in the specimen tip of the specimen holder being located in the column of the microscope. At this point, the barrel of the specimen holder bridges the space between the inside of the microscope and the outside of the load lock, and the end of the specimen holder is outside the microscope. To maintain an ultra-high vacuum environment inside the electron microscope, flexible o-rings are typically found along the barrel of the specimen holder, and these o-rings seal against the microscope when the specimen holder is inserted. The exact shape and size of the specimen holder varies with the type and manufacturer of the electron microscope, but each holder contains these three key regions.
The specimen holder can also be used to provide stimulus to the specimen, and this stimulus can include temperature (heating or cooling), electrical (e.g., applying a voltage or current), mechanical (e.g., applying stress or strain), chemical (e.g., containing a sample in a specific chemical environment), gas (e.g. containing a sample in a specific gaseous environment) or several at once. For example, an electrical power supply can generate a current or voltage waveform, while a syringe pump can be used hold and force liquids. This equipment is outside of the microscope, and various connectors are used to bring this stimulus to the holder, down the length of the holder, and to the samples. For example, microfluidic tubing can be used to supply liquids from the syringe pump to the sample, while electrical wires can be used to supply voltage/current. The specimen holder can also be used to deliver electrical signals measured from a sensor near the sample or the sample itself (e.g., electrical currents and/or voltages).
It is an object of the present invention to introduce an electron microscopy holder especially designed for in situ electrical stimuli and/or measurements, wherein said holder is improved to minimize electrical noise so that signal integrity can be maintained.